In general, to achieve a storage system having a large amount of capacity, it is necessary to configure a plurality of RAID (Redundant Array of Independent (or Inexpensive) Disks) groups composed of a large number of drives and generate one or more LUs (Logical Units) on each of the RAID groups. According to the PTL 1 for instance, a plurality of disk devices are coupled with a shared channel network and an element server accesses a disk device that is coupled with the shared channel network.